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Need some advice TIG welding patch panels

In a few areas on my car I have used my MM210 Mig to weld in patch panels on the car, tacking every inch or so, jumping around and letting it cool. This has worked, but I was not crazy about all the grinding that needed to be done afterward (maybe caused by my lack of experience).

So I was tacking a patch panel in on Saturday on my rusty quarter panel with the Mig and thought "I wonder if the Tig machine would do this a little cleaner"

So before I move forward to use my new Tig machine on the panel, I plan on practicing a good amount on some scrap sheetmetal of similar thickness. My question: is there anything I should do specifically in Tigging thin body panels? For example, is it best to tack similar to Mig, or run a continuous bead with the Tig? I realize heat is the enemy here and do not want to warp the panel, but was concerned that even a real low amperage setting may warp the panel with a continous bead.

TIG will have less to grind down, but you need the panels to fit TIGHT to do this. (like 0 gap) Practicing on scrap is always the best idea. This way you can get a good setting before you tackle the real thing. But, even with less amps you can warp the panel using TIG compared to MIG. The main reason is speed. The MIG is done as soon as you pull the trigger for tack welds. The TIG can take twice as long to tack for the novice. Even with the TIG you can't run long beads on thin stuff. Having a wet rag next to you to dab the weld right afterwards helps some, but can make the metal brittle if too much heat was applied.

Do you have .023 wire in your MIG? It works the best for body panels. For grinding down the weld I use a thin (3/32nd thick) cut off wheel in a die grinder, but a 4 1/2" angle grinder with a cut off works also. This way you only remove the filler not the metal in the panel, and it keeps the heat down.

Thanks. Yeah, I have been using .023 wire in the Mig. Good tip on grinding, will have to try that. I just figured this was a perfect application for me to put the new machine to use on. I realize it will be slower, but if the end product is better or at least less painful to get to (ex:less grinding), I thought it would be worth it.

If you are tig welding in patches On your ''rusty quartepanel'' you better cut your panel back to clean steel if you plan on making good welds with tig. The areas where you plan to attach donor panels to will probably have some porosity and contamination which will defeat the purpose of tigging them.You are going to fiind out first hand why body shops use mig instead of tig.if tiigging was the way to go more shops would do it.Also butt welded panels have to be fit up perfect or you will burn lots of holes trying to get a puddle started,If the fit up is perfect you can make some very nice precision welds on 18 guage.Just think that if the grinding is getting to you,how about the Body filler and 2K block sanding you will have to do to get the panel smooth? I dont think the tigging is the answer that you may think it is for auto sheetmetal.Mike

The blocking and priming isn't an issue. Not that I dislike the grinding, just makes me nervous that I spent a lot of careful time trying not to distort the area during the welding process that I am afraid I will create too much heat during grinding. I have seen it happen on a friend's car. For some reason he did not realize the amount of heat that builds up, had to do a lot of hammer/dolly work to get it back. I figured the Tig may help reduce that chance, but you do bring up some really good points.

I have the Tig machine right next to the Mig, so I will practice on a couple of scraps at first and see how I feel. May not even mess with it on the car if I do not feel comfortable.

I use both mig and tig for body panels. I prefer the tig for small patches and mig for larger work like quarter panels and floors.
I also like the 4 1/2 flapper disk over the grinding disk, it also helps to move around while grinding just like you do when welding.
Hope this helps DD

All great advice, thanks guys. This coming weekend I will mess with both. Since I have one part of the quarter already patched using the Mig, I still have to grind down the welds and will using the advice you guys provided. I will also spend some time messing with some thin scraps with the Tig and see how I do. Who knows, maybe it will work out better for me, at least it will give me more of a reason to tell the wife I need to go out in the garage to practice more